Speculations

We have no idea about why Roshni takes on the Diya name but we all have speculations. I am thinking that she might have blamed Sid for DD's death. I think in a short time she realizes that Sid was not at fault. It was not in his hands and that he tried to save her but couldn't. She might have been on her way to apologize but Amol might stop her and then blackmail her regarding Sid and harming him. He might have made something happen which could hurt Sid and show a video of it. Because of it Roshni realizes that she has to leave him forever and not be a part of his life again. So she leaves and then acts like Diya so Sid is unable to get her back and keeps his distance. I am almost 100% sure that Diya is none other than Roshni. I just can't figure her to either have real ML or be someone other than herself.